Relaxing with a good book in a warm home would be a lot more peaceful if it wasn’t for the screeching, squealing, rattling, or buzzing noises coming out of your gas furnace every time the air turns on. You’re grateful for the heat when the outside temperatures are frigid, but does the furnace need to continually make its presence known in the loudest way possible? Not when your repair partner is Repair Clinic. In this article, Repair Clinic has identified four primary causes of a loud or noisy furnace and how you can fix the unit so your home can be both comfortable and quiet.
Understanding where the furnace noise originates
When you understand how a gas furnace operates, you’ll have a better idea of where that annoying noise is originating from. Let’s start at the beginning of the furnace’s timed ignition sequence.
The gas furnace’s timed ignition sequence begins with the home’s thermostat
When the home’s thermostat calls for heat, the gas furnace goes through a timed ignition sequence that is initiated when the circuit board (AKA control board) sends 120 volts of alternating current to the furnace’s draft inducer fan motor. The inducer fan motor draws air into the burner assembly and, when the fan motor reaches its maximum speed, a vacuum switch is closed which ensures that gas will not enter the furnace unless the toxic fumes can be exhausted properly. Once the vacuum switch closes, 24 volts will travel through the switch, and one or more limit switches, allowing the circuit board to continue the combustion sequence.
Igniting the gas to create the heat
Depending on the furnace model, the next step in the sequence has the control board sending 120 volts of alternating current to a glow-bar style igniter or a greater amount of voltage to a spark igniter. The glow-bar style igniter will begin to heat up and will literally begin to glow orange, whereas a spark igniter will begin to pulse to create a spark. At this point, the circuit board will send 24 volts to the gas valve, opening it and allowing gas to flow over the igniter where the gas is ignited into a flame.
The circulation blower fan motor helps spread the heat throughout the home
Once the combustion sequence is successfully initiated, the control board will send 120 volts of alternating current to the circulation blower fan motor. A blower wheel fan attached to the motor shaft will draw air through the return vent, blow it past the heat exchanger, and force the now-heated air through the venting to spread the heat throughout the home, keeping you and your family comfortable when the outside weather is chilly.
The 4 reasons your furnace is loud or noisy
As you might have guessed that loud, annoying noise coming from your furnace is likely related to an issue with one of the fan motors. Below is a list of common noises that can emanate from the furnace and the parts that are probably responsible for that noise:
- Annoying squeaking or rattling – Are you hearing a squeaking or rattling sound when the furnace blower is running? That annoyance could be caused by a loose blower wheel set screw. The blower wheel is secured to the circulation blower fan motor shaft by the set screw. Vibrations caused by the blower motor running can loosen the screw causing the blower wheel to wobble on the shaft, resulting in a squeaking or rattling noise. First, try tightening the set screw. If the screw won’t hold the blower wheel in place securely, the screw could be stripped. If this is the case, you can often install a new set screw to fix the problem.
- Irritating squealing – Has the noise progressed from an annoying squeak to an irritating squeal? Then you should inspect the circulation blower wheel itself for damage. A damaged blower wheel can come into contact with the circulation blower motor housing causing a squealing sound as it rotates. As with the set screw, a damaged blower wheel should be replaced with a new one.
- Unsettling buzzing, screeching, or shrieking – Over time, the bearings inside the circulation blower fan motor can wear out. If the bearings are just beginning to fail, the motor may make a buzzing sound. However, this can progress to a louder screeching or shrieking noise if the bearings are getting ready to fail completely. Try rotating the blower wheel by hand to determine if it can turn freely or not. Do you hear a rattling or grinding sound when rotating the blower wheel? If the blower wheel is difficult to turn by hand or produces a noise when being turned, then you can be pretty sure the motor bearings are worn out. While some older furnace motors can be lubricated to reduce the noise, most current motors do not allow this, so if your furnace is a more recent model, you’ll need to install a new circulation blower fan motor to fix the unit.
The draft inducer fan motor bearings can wear out as well and produce the same unsettling noises. As with the circulation blower fan motor, a noisy draft inducer fan motor should be replaced with a new one.
- Incessant clicking – Are you at your wits’ end all because of an incessant clicking noise coming from your furnace? That’s normally the sound of the control board attempting to begin the ignition sequence, but if you’re hearing the sound repeatedly then it’s likely the board is shorting. If a condensation tube cracks, water from the tube could drip into the furnace cabinet and onto the circuit board which can cause the shorting and the accompanying clicking sound. If the board appears otherwise undamaged, you may be able to repair or replace the condensation tube and allow the board to dry before using the furnace again. However, if the control board is permanently shorted then you’ll need to install a new board to fix the furnace.
If you need to install a new blower wheel, circulation blower fan motor, draft inducer fan motor, or control board to keep your furnace operating effectively and quietly, it’s best to use the genuine manufacturer replacement parts specifically designed to work with your furnace. You’ll find those OEM parts at Repair Clinic.com. Whether your furnace is a Bryant, Lennox, Goodman, Rheem, York, Coleman, Ruud, Heil, or Payne model, just enter the full model number of the unit in the Repair Clinic website’s “Search Parts Online & Get Answers” search bar to see a comprehensive list of compatible parts. You can then use the “Part Category” navigation filter (example: “Motor”) followed by the “Part Title” navigation filter (example: “Draft Inducer Motor”) to refine that list to identify the exact part you need for your repair.
Repair Clinic has the resources to fix your furnace
With the right part in hand, you may need some assistance to properly install it. Whether it’s demonstrating the right way to replace a circulation blower wheel on a Payne (model PG9YAB048080AAA) furnace or showing, step-by-step, how to install a new draft inducer fan motor on a York (model G9S080B12MP11A) unit, Repair Clinic has the resources to fix your furnace. You can explore thousands of procedural and troubleshooting videos, step-by-step text guides, diagrams, and schematics covering all major home appliances, heating and cooling systems, and outdoor power equipment. Just select the product you need repair help with and let Repair Clinic show you how.